incubation

In developmental biology, incubation is a process of maintaining stable, warm conditions to ensure that eggs
develop and hatch. It is carried out naturally by birds and
by some reptiles. It is accomplished by sitting on the eggs, by making
use of volcanic or solar heat or the warmth of decaying vegetation,
or by covering the eggs with an insulating layer of sand or soil.

In microbiology, incubation is a method of keeping microorganisms, such as bacteria or viruses, warm and in an appropriate
medium to promote their growth (e.g., in identification of the organisms
causing disease); also the period during which the organism is present
in the body before causing disease (see incubation
period). Infectious disease is contracted from a source of infective microorganisms. Once these
have entered the body they divide and spread to different parts and
it is some time before they cause symptoms due to local or systemic
effects.